Organic light emitting diodes (OLEDs) have been widely utilized in displays. An AMOLED display uses a driving circuit to drive a light emitting element, i.e. an OLED. The AMOLED driving circuit uses TFTs, including a switch TFT and a driving TFT. The switch TFT, which is implemented by an N-type TFT (NTFT), is used for switching the ON/OFF state of a sub-pixel of the display. The driving TFT, which is implemented by a P-type TFT (PTFT), is used for driving the light emitting element (e.g. an OLED). In addition, a peripheral circuit of the AMOLED display also needs to use NTFT and PTFT. Conventionally, polycrystalline silicon (also referred to as poly-silicon) used in the TFTs of the AMOLED driving circuit and peripheral circuit is made by using a standard laser crystallization method to lead amorphous silicon growing on a glass substrate to crystallize into poly-silicon. Not like a silicon wafer used for manufacturing general transistors, the glass substrate suitable for a flat display cannot endure high temperatures, and therefore it is required to use a crystallization technique in which the temperature is lower than the melting temperature of glass substrate. Accordingly, the standard laser crystallization method is used. However, the standard laser crystallization technique has a problem. During triggering crystallization, output laser energy errors will result in a luminance non-uniform phenomenon called “mura” in the resultant display.
Further, the AMOLED driving TFT drives the OLED by an output current. The light emitting result is very sensitive to the variation in the driving current. A display area has a driving TFT matrix for a plurality of sub-pixels. If there are differences among the electrical properties of the respective driving TFTs, then light intensities of OLEDs in this area will have corresponding differences, resulting in visible distinction for human's vision.
After being made into a display, standard laser technique, current driving and the like factors regarding the driving TFT may result in stripe mura, thereby causing the yield of AMOLED products to be low. The present invention is to solve such a problem.